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You will be required to complete a 9KM return walk and or a Helicopter flight, which can be booked close to the Mitchell Falls National Park camp site. If booking a one way return flight, you will need to allow at least 2 hours to walk in and 3/4 hour to complete the Cache before your pick up. I chose to catch the Helicopter in and walk out. It was the last weekend in July and the temperature was in the low thirties.
The area is managed by Western Australian Department of Parks and Wildlife. Please obey the instructions on the signage and in their brochures.
The current landscape of the Kimberley has been evolving over a period of at least 250 million years. Periods of uplift resulted in peneplanation of the land surface and deeply incised rivers. A lengthy period of tropical conditions 70-50 million years ago resulted in the development of a lateritic cap, particularly over the volcanic rocks which are more susceptible to weathering. This is a characteristic feature of the Mitchell Plateau and very evident at WP3.
The geology of the Kimberley coast is diverse, ranging from sandy plains on the Dampier Peninsular, to basalt intrusions, granites and the rocky sandstone cliff faces and steep gorges on the central Kimberley coast. The rocks of the Kimberley region contain a geological record that spans the last 1900 million years of the Earth's history.
Approximately 2 billion years ago the Kimberley Plateau was formed when its underlying continent crashed into the Australian continent. This caused the uplifting of ranges, which were then eroded by an enormous river which carried sedimentary deposits to a shallow sea. These deposits became the Kimberley sandstones, siltstones and mudstones.
From 1.8 billion years ago, sandstone was laid down in several sequences, known as the King Leopold, Warton and Tertiary sequences. These Kimberley sandstones are up to 5km thick in parts. They can be clearly identified in the geological feature refered to in Q7.
Periods of uplifting then led to erosion, and huge outpourings of basalt, particularly around the Mitchell Plateau and Ord River Basin. Dolerite intrusions formed dykes, which are still evident in the King Leopold Ranges, and visible from Secure Bay, and on various islands along the coast. During these turbulent periods of uplifting, volcanic activity pushed lava and magma into cracks in the sandstones, forming veins of crystalized quartz. Some can be seen at WP1.
The main part of the Kimberley, known as the Kimberley Plateau comprises of generally flat lying sedimentary rocks. These sandstones and quartzites were deposited about 1800 million years ago by major river systems that flowed from north to south across the whole region. These rocks also contain considerable volumes of concordant basalt lava flows that are a characteristic of the Mitchell Plateau. Subsequent to around 1790 million years ago the region has seen several periods of geological activity that has resulted in deposition of further sedimentary sequences, largely around the margins of the Kimberley Plateau, and there is evidence for periods of major glaciations. One of which you are asked to comment on at WP2.
Approximately 5 million years ago there was another period of uplifting and layering, followed by the drowning of the coastline approximately 0.017 million years ago, forming the coastline as we now know it. As sea levels rose from approximately 120m below current levels following the end of the last glacial maxima 18,000 years ago, the Kimberley coast line became drowned with the sea filling what were once river valleys. This phenomena gives the coastline its distinctive irregular outline.
Well done Sprunghörnchen for being FTF.
WP1.
S14 49.442 E125 41.827 (Take care near the CLIFF).
After a pleasant walk, you have reached your first Geological features that will build towards your experience on the Plateau.
Q1. At this location, you will find 2 Geological features, one in front and the other behind you. Please describe them.
WP2.
S14 49.287 E125 41.555
You have just stepped onto the river bed and want to go further to see the Falls. Not so fast, there's 2 locations to examine first. It is also close to here that you will find the best swimming hole.
While here, take a look at the river bed at your feet and you will notice something different.
Q2. What is it that you can see.
Q3. Which direction does it run.
WP3.
S14 49.310 E125 41.607
You are now on the river bed above the falls and have a chance to take in some of the many Geological features.
Q4. How would you describe the grain, texture and colours of the rock in the area around where you are standing.
Q5. What does the black colour covering the rocks represent.
WP4.
S14 49.256 E125 41.757 (Take care near the CLIFF).
Now this is where you take in the majesty presented by Mother Nature. It is more than likely that visiting Mitchell Falls was your primary reason for talking the walk and logging a Earth Cache is a bonus.
Q6. How many Pools are visible at the time of your visit and how was this feature formed.
Q7. Looking SE, what Geological feature exists and what are the layers known as.
Walking back to the start of the return walk or Helicopter departure point, you can observe at least 3 different types of vegetation that have adapted to living in this environment. You can log a find immediately but must convey the answers to the CO via message within a week or two. If you fail to provide answers, you risk having your find log deleted.